Objective
The project aims at investigating the molecular mechanisms of solar energy conversion in natural photosynthesis, and applying the knowledge gained at constructing a prototype biomimetic supramolecular photochemical cell. The photosynthetic mechanisms comprise transfer of excitation energy to the photochemical reaction centre pigment-protein, followed by charge separation in this reaction centre (which converts the photon energy in the chemical free energy of separated electrical charges). The charges are then stabilised through dark electron transport along one or more chains of electron transport components (the so-called cofactors, which are embedded in the reaction centre protein). The energy of four accumulated positive charges is then used for water oxidation, producing four protons and molecular oxygen.
The project focuses on elucidating the interactions between the energy and electron transfer components themselves, and between these components and the surrounding protein matrix. The interactions between the cofactors themselves are responsible for the amazingly efficient energy and electron transfer processes found in all photosynthetic systems, which convert and store solar energy in chemical free energy with an efficiency that is 4 to 5 times higher than the most efficient man-made device.
The interactions with the protein matrix have two important functions:
1. They modify the properties of otherwise identical cofactors, conferring on them quite different functional properties;
2. They play a crucial role in the dynamics of energy and electron transfer. The research goal is approached using a variety of biophysical and biochemical techniques, such as sophisticated optical and magnetic resonance spectroscopic methods, special preparative procedures, cofactor modification and exchange, isotope labelling, site-directed mutagenesis. These techniques are applied to a number of different photosynthetic systems of bacterial and plant origin. In this way common crucial features of the energy conversion process will be assessed.
Our second objective is the construction of a simple self-organising photochemical device that mimics the first crucial steps of biological photo-energy conversion in oxygen-evolving plants, to wit charge separation from a photo-excited sensitiser molecule, subsequent charge stabilisation, and finally charge storage on a manganese-complex. Pursuing the two objectives in parallel will allow us to continually cross-reference results and questions arising from the two lines of research, thus achieving optimal synergism.
Expected results comprise: For interactions, the quantitative determination of the exchange and dipolar interactions between electron transfer cofactors, the determination of the role the protein matrix plays in electron transfer and in charge stabilisation, the determination of cofactor-protein interactions in the cofactor binding pocket, the investigation of the way these interactions modify cofactor properties. For biomimetic photochemistry, the construction of a supramolecular assembly composed of a photo-oxidisable sensitizer, a charge-stabilising chain that contains one or several oxidisable linker molecules, and a charge-storage system containing two or more Mn ions.
The results of the present research project will make an important contribution towards a full understanding of natural solar energy conversion at the molecular level and to translate such understanding into practical, biomimetic systems for solar energy conversion.
Topic(s)
Call for proposal
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2300 RA Leiden
Netherlands